The ultimate objective of this program is cure of children with leukemia. The program is a coordinated effort of therapy and study including: therapeutic trials; studies of biology and pathogenesis; and studies of effects of leukemia and therapy on normal tissues. The program consists of a core section and 7 interrelated projects: the core section provides for resource personnel, patient costs, leukemia cell profile studies, biostatistics and a patient data base to be used by virtually all projects. The projects are: (1) primary therapy of acute lymphocytic leukemia; (2) primary therapy of acute nonlymphocytic leukemia; (4) leukemia cell kinetics; (5) studies of in vitro growth of normal and leukemic marrow; (6) studies of hemopoietic effects of leukemia in animals; and (7) late effects of childhood leukemia. All projects except number 6 involve patients or patient materials. All projects have the same ultimate objective through a wide variety of disciplines. The organizational structure provides the means for a unified and coordinated effort.